Hundreds of Martian craters have been identified as possible fossil lakes, based on the presence of now dry channels or sediments deposited at former deltas, said lead study author James Wray of Cornell University.

But new pictures from NASA's Mars Reconnaissance Orbiter have revealed that Columbus crater has alternating layers of hydrated minerals—clays and sulfates known to form only in the presence of water.

"Some lakes in western Australia that are relatively acidic and pretty salty show similar minerals to what we see in Columbus crater," Wray said.

What's more, the crater is one of the few proposed fossil lakes thought to have been fed entirely by groundwater, Wray added.

"If [the water] had come from rain, we would expect to see channels," Wray said. "But we don't."